Abstract
To assess the characteristics of positive blood cultures in a tertiary medical center in Japan, 332 positive blood culture episodes were reviewed from 241 patients at a university hospital in 2012. These episodes were considered to represent true bacteremia or contamination at the discretion of the judging panel in the hospital's department of infection control and prevention. The correlations were examined between episodes of true bacteremia or contamination, identities of isolated bacteria, time to positivity (TTP) of blood culture, underlying medical conditions, catheter placement, and antibiotic therapies. A total of 244 of 332 positive blood culture episodes (75.8%) represented true bacteremia. Microorganisms frequently found in true bacteremia were fungus (11/11, 100.0%), gram-negative rods (95/99, 96.0%), and Staphylococcus aureus (43/45, 95.6%), whereas coagulase-negative staphylococci (38/93, 40.9%) was less common. The mean TTP of blood cultures representing true bacteremia and contamination was 22.1 hours and 31.6 hours, respectively. The difference in TTP for each group was more than 10 hours for staphylococci and enterococci, although this trend was not observed for other microorganisms. Antibiotic therapy was administered in 156 of the 175 cases of true bacteremia. Among these cases, antibiotic therapy was initiated before performing blood culture in 43 cases, simultaneously with blood culture in 45 cases, after positive blood culture was reported in 50 cases, and when the identity or antibiotic susceptibility of the isolated microorganism was reported in 18 cases. These findings will facilitate the confirmation of true bacteremia in clinical settings, and, in combination with improvements in the laboratory reporting system, will improve future therapies for patients with bacteremia.
